Handling of bone cement in such surgery as replacement of hip joints is a crucial step. The mixing of bone cement components, a powder and a liquid (monomer), has to occur no more than about 30 seconds prior to application of the mixed bone cement, and the device used for mixing therefore needs to be simple and quick to handle.
WO-A-2010/002346 discloses a bone cement mixing device which has a piston displaceable in a cylinder, and a piston rod with a mixing member for mixing and subsequent dispension of the bone cement to the surgical area. Before use, a funnel is attached to the cylinder through which funnel the powder and the liquid are fed into the cylinder. During this filling, the device is placed vertically on a base member with the funnel upwards. In a following step, the funnel and the base member are removed and the free end of the cylinder is closed, prior to mixing. After mixing of the bone cement components, a dispensing tube is connected to the free end of the cylinder and used for applying the bone cement to the operative area, e. g. a joint. This mixing and dispensing device has been tested in practice with good results. However, there is still room for improvements. The filling, mixing and dispensing of bone cement involve several steps of adding components as well as connecting and removing parts to the cylinder. Although performed within the time limit of 30 seconds, these steps are time-consuming and somewhat stressful for the user.
Another type of bone cement mixer/dispenser is known from EP-A-1,741,413 where the powder is contained inside a mixing container and the liquid is kept in liquid containers extending alongside the mixing container. The liquid containers are then opened by means of a cannula through which the liquid flows into the mixing container to be mixed with the powder by a piston rod. This method of delivering the liquid to the container requires additional equipment in the form of two brackets alongside the mixing container which hold the liquid containers. A drawback of this mixer/dispenser and similar solutions is that the brackets take up a large proportion of the external portion of the mixing container which makes this prior-art device bulky and difficult to operate. Also, the opening of the liquid containers sideways by cannulas requires an unnecessary complex structure. For instance, if only one liquid container is to be emptied, the structure involves the addition of a cap at the cannula not to be used. The cap prevents the sealing means of the cannula from loosening during handling.
A further example of a bone cement dispensing device is disclosed in U.S. Pat. No. 6,796,701 which basically suffers from the same drawbacks as discussed above.
From the above, it is evident that there is room for improvements of prior-art mixing and dispensing devices of this kind.